Tracking and position control of an MRI-powered needle-insertion robot

The excellent imaging capabilities of MRI technology are standardizing this modality for a variety of interventional procedures. To assist radiologists, MRI compatible robots relying on traditional actuation technologies are being developed. Recently, a robot that is not only MRI compatible but also MRI powered was introduced. This surgical robot is imaged and actuated through interleaved MRI pulses, and can be controlled to perform automated needle insertion. Using the electromagnetic field generated by the MRI scanner, the robot can exercise adequate forces to puncture tissue. Towards the goal of automation, this paper reports results on tracking and control of an MRI-powered robot tagged with a fiducial marker. Tracking is achieved using non-selective RF pulses and balanced gradient readouts. To suppress the signal received from the tissue, spoiler gradients and background suppression are introduced. Their effects on tracking are quantified and are used to optimize the algorithm. Subsequently, a Kalman filter is employed for robustness. The developed algorithm is used to demonstrate position controlled needle insertion ex vivo.